Tim Harris from the Wren Wildlife Group describes some of our most fascinating insects: dragonflies and damselflies, which thrive in Wanstead Park, like this four-spotted chaser photographed at Perch Pond
Take a stroll along one of the lakes in Wanstead Park on any warm, sunny day from May to October and you have a very good chance of seeing one of our many local dragonflies or damselflies – perched on a lily pad, grasping an iris blade, sunning itself on a path, or whizzing past in pursuit of prey.
Collectively known as the Odonata, according to fossil records, these flying insects have been around for some 350 million years. There are 46 species in the UK, and 21 have reliably been seen in Wanstead.
Unless we take up pond dipping, we only see the last and shortest stage of their fascinating life cycle. Dragonflies and damselflies undergo incomplete metamorphosis with three life stages, rather than butterflies’ four: egg, larva, and adult. Fertilised females inject many tiny eggs into aquatic vegetation near the water surface, or – depending on the species – deposit them loosely in water. Within a few weeks, the eggs hatch into larvae. This is the longest stage of a dragonfly’s life. Over the course of one, two, or even five years in the case of the golden-ringed dragonfly, they are active underwater predators in freshwater lakes and rivers. As they grow, the larvae are able to eat ever-larger prey, including other insects, snails, leeches, tadpoles and even small fish.
When they are ready, the larvae climb out of the water and up the stalk of an aquatic plant and squeeze themselves out of their larval ‘skin’. Sometimes, these discarded exuviae can be found still attached to vegetation. The newly emerged adult dries its wings and legs in the sun and, when strong enough, takes its first tentative flight.
The first species to emerge locally is the large red damselfly, which can sometimes be seen by tiny garden ponds in late April, while common and ruddy darters can even be seen on warm days in October. Adults typically live no more than a fortnight, though some may fly for eight weeks before they perish. If they successfully mate during this time, they will have kick-started another generation.
In Wanstead Park, the margins of Shoulder of Mutton, Heronry, and Perch ponds are alive with these colourful insects on warm summer days; the bank at the east end of Perch Pond is as good a place as any to watch a variety of behaviours. There, aggressive male dragonflies can be seen chasing off rivals, while females lay their eggs among the waterside plants. And sometimes, dozens of coupled pairs of damselflies can be seen mating on the wing or on mats of weed.
With global climate change, some continental species are colonising southern England. Others seem to be struggling. In our area, they have both unpolluted water and emergent vegetation, and that’s why they’re thriving. If you see anything interesting, you can report your sighting to the British Dragonfly Society (BDS). Better still, join the BDS and help their efforts to conserve these beautiful creatures.
For more information on the British Dragonfly Society, visit wnstd.com/bds
For more information on the Wren Wildlife Group, visit wnstd.com/wren